Pursuant to the recent developments in computer graphics technology, simulation devices and game devices have become widely popular for both business and domestic use. As one genre of this game device, there is a role playing game (hereinafter referred to as “RPG”) wherein a story is commenced in a virtual three-dimensional space (also referred to as a game space), a character simulating the player plays a prescribed game at various important points in the story and, in accordance with the game results, progresses the game while changing the game development for each such occasion. RPGs have gained popularity for presenting different effects than the other more competition games or battle games.
Game devices conducting such RPGs perform the various image processing described below in order to secure the game amusement and conduct vast loads of game operations.
As the first processing, there is a method of changing the color and appearance of the sky in accordance with the time period the player is to play the game. This processing, for example, is conducted by the CPU inside the game device reading image data or parameter representing the background sky upon referring to a table based on the clock value of the internal clock, and displaying this read image data, or, displaying the image data corresponding to the read parameter. Thereby, attempted is the creation of a game space as real as possible in order to evoke the interest of players.
As the second processing, in the case of a game device for conducting RPGs, a player receives operational information at important points (strategic positions) during the game development and, for example, interactively implements an action game (manual mode) on the one hand, and the story for connecting such important points are compulsorily advanced (auto mode) by the CPU since it is necessary to advance the story in view of the characteristics of RPGs. Thereby, it is possible to secure the storyline in consideration of the game being an RPG.
As the third processing, with respect to the image display of the game device, generally, objects are formed of polygons and displayed. Thus, more the polygons, increased is the operational load for operating the displayed state, and the CPU processing will become heavy. Here, generally, objects outside the display range of the monitor; that is, objects positioned on the outside of the visual field range seen from a virtual camera viewpoint on the game space, are not displayed. Moreover, upon a three-dimensional (polygon) display, to objects positioned afar exceeding a prescribed distance on the screen, clipping processing (far-clipping processing) for non-operation of such display data is performed. Furthermore, processing using the z-value sorting method for not displaying a polygon behind a certain polygon when seen from a viewpoint; i.e., shadow-face processing, is implemented in polygon units that form the object.
As the fourth processing, there is a process of laying out rooms (partitioned space) inside a building (house, warehouse, remains of a building, etc.), which is often required upon providing the game environment of RPGs. With respect to this layout, which object is arranged at which position in the room is determined, all rooms are previously laid out, and such layout data is stored in the memory. Further, upon creating polygons of maps (caves, tunnels) for the character to move in games such as an RPG, shapes were previously set in the respective polygon units, and stored in the memory as polygon data.
Although a certain degree of effect can be obtained in reply to the needs of wanting to provide images full of reality and ambience, and securing a certain game amusement pursuant to the various image processing described above, it can in no way be said that this was sufficient.
For example, with the aforementioned first image processing that changes the color and appearance of the sky in accordance with the time period, it is possible to provide the player with a sense of time, such as daytime or evening, to a certain degree. Nevertheless, the natural environment of the outside is not determined only with the control of the display mode of the sky, and demanded is a display of a more realistic natural environment.
In the case of the second image processing, the ratio of the storyline (auto mode) as an RPG and the action (manual mode) for playing an action game is determined in advance. Thus, it lacks versatility in terms of the player not being able to change between the modes in accordance with his/her feelings at such time, and it is also unadaptable in terms of the game device provider not being able to, after manufacture thereof, ship the game upon changing the ratio in accordance with the characteristics of the market. The length of the game processed in real time between the player; i.e., the manual mode, is one factor that reflects on the difficulty of the game. Therefore, it also means that there will be less selectivity for setting the difficulty of the game.
With only the clipping and shadow-face processing of polygons according to the third image processing, the operational load pursuant to the judgment of the display/non-display is still heavy, and there are many demands for the improvement of high-speed processing by lightening the operational load.
For instance, in a role-playing game, presume a scene where Godzilla strays about in an area having a number of towering buildings and it is to fight the player. The respective buildings are objects created with polygon data and treated as a part of the background, and Godzilla is also treated as one character object created with polygon data. In this scene, if Godzilla is positioned in front of the buildings, performing rendering processing for displaying Godzilla with the buildings as the background is natural, but it is not necessary to display Godzilla when it is completely hidden behind a building. Nonetheless, with a conventional shadow-face device, the Z value must be obtained in polygon units with the Z-sorting method regarding the hidden Godzilla and the buildings, and compared thereafter. This Z value comparison in polygon units among objects considerably increases the operational load. When the load is heavy pursuant to the shadow-face processing as described above, unless the processing speed of the CPU itself is increased, the operational capacity which may be transferred to other game processing will be reduced. Further, even if the rendering processing can be lightened with the Z-sorting method, the geometry processing at the previous stage will still not be lightened, and sufficient image display cannot be expected with only the above.
In the case of the fourth image processing, the layout of the rooms requires a vast operational load. Thus, adopted were methods such as not allowing the entrance into a room where no event occurs or seeking simplification of the operation by making the layout of the respective rooms the same. This, however, causes an extremely unnatural feeling to the player. Although it would be possible to use similar patterns for the layout process to a certain degree, if the environment of the rooms is similar, rooms resembling each other will be created. This will be one cause for a player losing interest in the game. Upon preparing a map, the larger the map, the operational load necessary for such preparation will be vast as a matter of course, and it is further necessary to secure a memory with a large storage size. If the memory or transmission path is a disk medium or telephone circuit having a comparatively slow reading speed, or if the storage size of the memory for storing the read data is small, the reading time and reading frequency will increase, and this increase in processing gives dissatisfaction to the players.
The present invention was devised in view of the aforementioned circumstances encountered by the prior art, and the principle object thereof is to provide a game capable of reducing the operational load for judging the display/non-display of the object, is full of realism and ambience, and which enables variations in the difficulty of the game in accordance with the preference of the player.
Particularly, the first concrete object is to sharply reduce the operational load consequent upon the display/non-display of an object with simple processing in consideration of the position relationship from the viewpoint from the object and the background.
Moreover, the second concrete object is to enable layouts and preparations thereof utilizing the analog sensitiveness of human beings as well as simultaneously substantially reducing the operational load in games requiring the preparation of layouts of rooms and maps.
Further, the third concrete object is to provide a game having improved reality and ambience by precisely expressing the time changes of the outside natural environment.
In addition, the fourth concrete object is to enable changes in the difficulty of RPGs in accordance with the player's preference or the market situation at the time of shipment with respect to RPGs.